JEE Main · 2021 · 17 Mar 2021 · Shift 2 · Coordination Compounds

On complete reaction of

FeCl_{3}

with oxalic acid in aqueous solution containing KOH, resulted in the formation of product A. The secondary valency of Fe in the product A is ______.
(Round off to the nearest integer).

Answer: 6

Solution

Oxalic acid in the presence of potassium hydroxide supplies oxalate ions, which displace the chloride from iron(III) and give the complex

K_{3} [Fe (C_{2} O_{4})_{3}]

. Secondary valency is Werner's term for the coordination number, the number of donor atoms bonded directly to the metal. Oxalate is bidentate and binds through two of its oxygen atoms, so three oxalate ligands occupy

3 \times 2 = 6

coordination positions around the iron. The secondary valency of iron in the product is

6

JEE Main · 2021 · 17 Mar 2021 · Shift 2 · Integer answer

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